From patchwork Tue Jun 20 09:15:25 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiao Guangrong X-Patchwork-Id: 778186 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3wsMjP6gBCz9s4s for ; Tue, 20 Jun 2017 19:19:05 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="XCzep5NG"; dkim-atps=neutral Received: from localhost ([::1]:47456 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dNFJP-0001p5-JE for incoming@patchwork.ozlabs.org; Tue, 20 Jun 2017 05:19:03 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52999) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dNFGU-0000Fd-8j for qemu-devel@nongnu.org; Tue, 20 Jun 2017 05:16:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dNFGS-0007t9-4D for qemu-devel@nongnu.org; Tue, 20 Jun 2017 05:16:02 -0400 Received: from mail-pf0-x241.google.com ([2607:f8b0:400e:c00::241]:36553) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dNFGR-0007se-UH for qemu-devel@nongnu.org; Tue, 20 Jun 2017 05:16:00 -0400 Received: by mail-pf0-x241.google.com with SMTP id y7so21600713pfd.3 for ; Tue, 20 Jun 2017 02:15:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=DaNO5Ln0PEifPXwFkrDyQ2ovE8Tg5tNeAITmsZ8hO40=; b=XCzep5NGzXMSFNW5MW3OdJUrDfFRKLKoNeReGsM+fR0N9Os39VuBzTHyQ7IFD44fh1 lm06NRto+0nbeDpr/JRAZiKSUNyFPsmzX1E2s7WSitqTKjcGCyAEn3qNaMG3kTufCXaE SmgQZO0JRFB7H/btErz9/+llPhhAX9gdn9cSY/bd5rCJCkZms0x2u9c+t/8PmG2+QX64 Pr0LkF+eXTwtv/HdzPKzi7k0WZV7fOmDYv/FDjs6wge5UOrVoaWP/29cxRKye0YyXmTs xhOCZA3RjYronPlUn6dO9BaF8hHvl0Lj2Tsi3Zo4icR8RIdYegXHs4DaxVm0GhGe7w8O 8RWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=DaNO5Ln0PEifPXwFkrDyQ2ovE8Tg5tNeAITmsZ8hO40=; b=T/wUvku6U+M4MTGD9xnOkw15BIt40kaRW5N9l4s6rzBQNQIX0ICiYQJ+FQXu92DEVD PEYFdpGEk4kRqBmflCPjWqlcBpKzkGQsoshwgFAuhU2oBco4aHxz84GMrbJc5cJojEY5 RRu+oNdi/m9sLlaituno/QAemJNIHKH7EuMdIc1qkFy1hSWqVdkBNZJDWlrwT9XABn/a eaewjwQhajnHRMffDE2IeK62gzUig6uNUZAEBI484dflgo6AgbKlRX0U5q+XoeVoCgpp 0mVSU0JqWtQMWMYtq66GpLrqu618UAGkalafFWofxxag78KlDMd+WdCOGTuXF6F+2Gt+ GRkA== X-Gm-Message-State: AKS2vOzwb1Ba+OMTOxnEWUIKVIEBV9GfPVqBVkTSfdRU0QvdpJnXRHXM 7BxyGUyu2XzGEQ== X-Received: by 10.84.229.78 with SMTP id d14mr13395841pln.212.1497950159170; Tue, 20 Jun 2017 02:15:59 -0700 (PDT) Received: from eric.tencent.com ([203.205.141.35]) by smtp.gmail.com with ESMTPSA id o12sm26343810pfi.9.2017.06.20.02.15.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Jun 2017 02:15:58 -0700 (PDT) From: guangrong.xiao@gmail.com X-Google-Original-From: xiaoguangrong@tencent.com To: pbonzini@redhat.com, mtosatti@redhat.com, avi.kivity@gmail.com, rkrcmar@redhat.com Date: Tue, 20 Jun 2017 17:15:25 +0800 Message-Id: <20170620091526.4287-7-xiaoguangrong@tencent.com> X-Mailer: git-send-email 2.9.4 In-Reply-To: <20170620091526.4287-1-xiaoguangrong@tencent.com> References: <20170620091526.4287-1-xiaoguangrong@tencent.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:400e:c00::241 Subject: [Qemu-devel] [PATCH v2 6/7] KVM: MMU: clarify fast_pf_fix_direct_spte X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Xiao Guangrong , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Xiao Guangrong The writable spte can not be locklessly fixed and add a WARN_ON() to trigger the warning if something out of our mind happens, that is good for us to track if the log for writable spte is missed on the fast path Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index c011ab0..7711953 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3240,6 +3240,15 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, WARN_ON(!sp->role.direct); /* + * the original spte can not be writable as only the spte which + * fulfills is_access_track_spte() or + * spte_can_locklessly_be_made_writable() can be locklessly fixed, + * for the former, the W bit is always cleared, for the latter, + * there is nothing to do if it is already writable. + */ + WARN_ON(is_writable_pte(old_spte)); + + /* * Theoretically we could also set dirty bit (and flush TLB) here in * order to eliminate unnecessary PML logging. See comments in * set_spte. But fast_page_fault is very unlikely to happen with PML @@ -3254,7 +3263,7 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (cmpxchg64(sptep, old_spte, new_spte) != old_spte) return false; - if (is_writable_pte(new_spte) && !is_writable_pte(old_spte)) { + if (is_writable_pte(new_spte)) { /* * The gfn of direct spte is stable since it is * calculated by sp->gfn.